Concentration of chlorine



F. R. BALCAR CONCENTRATION OF CHLORINEv Aug. 24, 1948.

2 Sheets- Sheet 1 Filed April 15, 1944 HESQ 928 INVENTOR. fitderrk Bdfi'a Y a PM A TTOR NE Y5 Aug. 24, 1948. F. R. BALCAR I CONCENTRATION OF GHLORINE 2 Sheets-Sheet 2 Filed April 15, 1944 INVENTOR. ret/ens}? Bud- BY ATTORNEY/,5

Patented Aug. 24, 1948 CONCENTRATION OF CHLORINE Frederick R. Balcar, Stamford, Conn., assignor to Air Reduction Company, Incorporated, New York, N. Y., a corporation of New York Application April 15, 1944, SerialNo. 531,267 8 Claims. (01. 23 -219) I This invention relates to the concentration of dilute chlorine and particularly to the recovery of chlorine produced by catalytic oxidation of hydrogen chloride.

The 'productionof chlorine by the oxidation of hydrogen-chloride in the presence of a catalyst is well known. Pure oxygen may be used in the oxidation and affords a product free from other gases which can be recovered readily. Oxygen is, however, relatively expensive. The oxygen of the atmosphere is substantially equivalent as an oxidizing agent, but the product is necessarily contaminated with alarge proportion of nitrogen from which the chlorine must be separated.

Various conventional procedures are available for that purpose, but they involve greatexpense for initial cost and upkeep of the necessary apparatus. Moist chlorine, even at ordinary room temperature, attacks common metals rapidly, causing accelerated deterioration. Hence the use of pumps, compressors, blowers and all apparatus which cannot be constructed of corrosionproof materials or easily protected from the corrosive effect of chlorine must be avoided.

Water is known to. be a very poor solvent for chlorine. When saturated with chlorine gas in about 20% concentration, it will contain only about 0.1% by weight of chlorine. This amount is so small as to make the use of water as a solvent in chlorine recovery operations appear to be hopeless. The expelling of chlorine in commercial quantities from the large volume of water required to absorb it would be practically impossible according to conventional procedure. It would be necessary to provide relatively normous heat exchange surfaces resistant to the action of chlorine, andthe amount 'of steam required would be greater in cost than the value of the chlorine recovered. However, as will hereinafter appear, water can be used successfully to recover chlorine from gaseous mixtures of relatively low concentration.

, It is the object of the present invention to provide a relatively simple, economical and effective method of separating chlorine from gases such as nitrogen, with which it is mixed.

Another object of the invention is the provision of a method whereby water may be used effectively and economically in the separation of chlorine from gases such as nitrogen.

A further object of the invention is the provision of a method of separating chlorine from nitrogen and the like wherein apparatus with a minimum of moving parts and readily protectable from. corrosion can be utilized.

Other objects and advantages of the invention will be apparent as it is better understood by ref-.

erence to the following specification and the ace companying drawing, in which 1 Fig. 1 is a diagrammatic illustration of. apparatus suitable for the practice of the inventionf and v Fig. 2 is a similar view illustrating auxiliary equipment which can be employed to recover any residue of chlorine which escapes from the primary apparatus.

, In carrying out the invention, the dilute chlo rine is first absorbed in a relatively large volume of water, The nitrogen is thus separated and may be delivered to the atmosphere. Since it may be uneconomical to operate the apparatus so that much more than 90% of the chlorine present is' absorbed in the Water, it is preferable to employ auxiliary equipment. as hereinafter described in which the residual chlorine may be absorbed in milk of lime or equivalent material which will fix the chlorine and prevent escape ofthe residue to the atmosphere.

The water solution of chlorine is subjected to reduced pressure in successive steps to liberatethe chlorine therefrom. To maintain the reduced,

pressure, any suitable equipment may be employed, but I prefer to utilize steam jet evactors with accompanying condensers which permit delivery of the chlorine product at atmospheric pressure and a condensate consisting of water which may contain small percentages of chlorine. The condensed water is cycled in the system so that none of the chlorine is lost. A purge is provided to draw off an amount of water equivalent to the amountof steam employed inthe system.

The evactors may be constructed of any suitable corrosion resistant material such as porcelain, carbon or other acid-proof materials. Since these devices embody no moving parts, they can be constructed cheaply and operated with a minimum of maintenance cost. Other parts of the appa-- ratus which are likely to be afiected by moist chlorine can be suitably protected in the conventional manner to avoid damage thereto.

Referring to the drawing, 5 indicates a tower whichmay be packed with rings or other devices to facilitate increased surface contact between the liquid and gases flowing therethrough. The dilute chlorine mixed with nitrogen is introduced through a pipe 6 atthe bottom of the tower and flows upwardly therethrough in contact with water introduced through the pipe I. The nitrogen which is not absorbed escapes through the pipe 8. The water containing the dissolved chlorine The liquid in its descent through the tower l2 is subjected to reduced pressure. ""Th'e'rpressure employed may be such that the partial pressure of the chlorine in the vapors" inequilibrium'withthe liquid leaving the tower is approximately 3 one-half that of the partial pressure of chlorine in the vapor in equilibrium with the tliquidentera Under these conditions, about ing the tower. half of the chlorine entering the tower I2 is re-' moved as vapor and passes through the outlet pipefM to the-inlet '15 of the 'evactor' 16. "The latter comprises aninjector l I supplied with steam from a pipe 'l'athrough'a branch-I9 controlled by a valve and a Venturi tubeZ l' which is connected to .a'cond'enser-ZZ. Water is supplied tothe'condenserthrough a pipe-Hand withdrawn through a pipe 24. The amount of steamsupplied tothe evactor will be sufficient to maintain thedesired .reduced' pressure in the tower l2. The steam is'condensed'in the-condenser 22..and..the chlorine escapesthrough a pipe25. The condensate is withdrawn through a pipe 25.

The liquid from which approximately half the chlorine has'been removed in the tower I2 is delivered-by a pipel'l to .a second tower'28' which is .packed with rings or other devices as 'in the case-'of the tower l2. Steam is introduced" to the bottom of the towerf28 through'a pipe 29 in amount sufficientito. raise the temperature of the exit solutionto .a point where the: vaporpressure of the water is equal to the combined partial pressures .of .chlorine and water in 'the vaporin equilibrium withthe' inlet solution to theltower. Thlisatemperature. rise is ofthe order- .of buta few...degrees.. A reduced. pressure is maintained withinthe. tower- 2B,..such pressure being .at or slightly. above. thevapor x.pressure of the solvent at thehtemperature.involved. .As. a result, substantially. allotv thechlorineis removed from the liquid. andescapes through a pipe..30. .Theresidualsliquidewhich..in. some. instances, at least, will .includesome chlorine dissolved. in water, is withdrawn through apipe 3| and. is delivered byapump 3'2.-arld..pipew 33 tothe inlet. pipefl of thErI-OWBIi. =...A..purge..34.controlled.by a valve 35$.permits the withdrawal .of surplusliquid.

.The .necessary: reduced -pressure in the tower 28 .i maintained byxan. evactor 36 consisting of a ainjeotor 31..connected to the steam line [8 by a pipe.38 .-controlled bye-valve 39Iarid a Venturi tubefiflwhichtis .connected to a condenser 4|. W,ater...i supplied to the. condenser through; a pipe 42 andwithdrawnthrough apipe 43. T The chlorine. is deliveredby a pipe 44 to the inletpipe lief .the evactor I6. The condensate is delivered through a. pipe 45 to the pipe?! and thus returnedto the tower 28.. The chlorine deliveredby thepipe 25which includes all of the chlorineLseparated from"'the liquid in the towers l2 and 28,"enters an evactor 46 "donsistirigrofxam injector 41 connected to 'thesteam line"'|"8 by a pipe' lfl'controlled'bya valve w andfa Venturi' tube 50 which'ds connected to a condenser 5| 1 Water is supplied' to the con denser through a pipe 52 and withdrawn through a pipe 53. The amount of steam supplied is sufficient to bring the chlorine up to atmospheric pressure, and it is discharged through a pipe 54 and may be delivered to any suitable receptacle for storage. The condensate is delivered through a pipe 55 and is joined by the condensate from the pipe 26.". The combined"condensates'are delivered by a pipe 56 to the inlet of the pump l0 and thus combined with the liquid from the tower '5. This arrangement ensures against any substantiarl'rilossrof 'chlorine in the operation.

As an example of the application of the inventionfl shall-describe the recovery and concentration of about r'oneziton of chlorine per hour in accordance with the procedure. Gas containing approximately=20 %''.by volume of chlorine is fed to the bottom of the tower 5. About 200,000 gallons 'of'water per hour .are passed through the tower 5 at a temperature of about F. The resulting-dilute chlorine solution is pumpedto thetower l2, where itis subjected-to a reduced pressure 'of about mm. *oi'rnercury absolute with or without the addition of steam. As the partial pressure of'the chlorine in the original gas mixture entering the -tower*5 =will 'be -about 152 minof mercury,the'subjectionin the tower 5'2 of the dilute chlorine solution from the tower 5 to a lower pressure of about- 105mm. of mercury will insure 'vaporization'of' chlorine 'which is removed-through the pipe M. The vapors-removed through the pipe -I4 will contain about 1,000 pounds of chlorine'and'about-105 pounds of water per hour, and the water-Will be-condensed in the passes to the tower 28 wherein it is subjected to a pressure of about 40 mmxof'mercury absolute. The vapor from this tower escapingthrough the pipe30 will carry about -1,000'-pounds'of chlorine and 1,000 pounds of *water' per hour; The 'water will becondensed 'in the condenser -41. The evactor 36 will require about 2200 pounds per hour of steam.

The vapor from the condenser 4| joins the vaporfrom thetower l2 in the evactor l6. Hence about 2,000- pounds ofc'hlorine arid 210-p0unds of "water vapor per hour-"are delivered to the evactor 16 "which requires about 2500 pounds'of steam per hour. The vapors "leaving the condenser 22 will contain about 2,000 pounds of-chlo rine and" pounds of 'water 'per hour, and the evactor 46 will require 4,000 pounds of steam per hour to'deliver at atmospheric pressure'approxi mate ly2;000 pounds of high purity chlorine. In addition to thesteamintroduce'd to the evactors,

through the; pipe 29 to tmainizaintherm'al balance in the system. The additions" of steam -require the;purging of-the" system" through the pipe34 as hereinbefore "indicated to avoid excess 'water.

in the system.

When it is desired to recover residual chlorine whicn'may escape from the. tower 5;1. providea pipe 51 connected to thetopof. the tower aridzto an absorber 58,'which'may be supplied with milk of lime or other absorbin'g material through a pipe 59 "controlled bya valve 60." "Anagitator 6 I, driven by a motor 62 or other convenient means; ensuresadequate contact "of "the' gas with =the" absorbent material. The "residual "chlorine "is fixed by combination-with-calcium and the nitrogen" escapes'througha pipe 63. The-'contentsof the" absorber may-be withdrawn from time to 75 valve 65,

to high temperatures may be of rubber-lined construction or of any other material adapted to resist the corrosive effect of chlorine. Packing for the towers may be of ceramic or carbon materials. As already indicated; the evactors may be of similar material. Hence the entire system can be constructed so as to prevent'corrosion or deterioration as a result of contact with chlorine. Although I have shown indirect condensers in con nection with the-evactors, direct coolers may be substituted therefor if desired.

The amount of chlorine vapors leaving tower may be controlled by-varying the amount of water entering the tower,by varying the pressures in the towers I2 and 28, or the amount of steam fed to the towers i2 and 28. In this manner the amount of chlorine available for the production of hypochlorite may be adjusted'to give the desired ratio between chlorine and'hypoch'lorite as thefinal products of the operation. I

In general the higher the total pressure at which the gases enter the various evactors, the smaller will be the proportion of water present, and the smaller will be the amount of motive steam required in the evactors. Since theuseof motive steam for compress-ingwater vapor rep resents a waste ofenergy; it is advantageous to operate in a manner that will make the water vapor entering the evactors a minimum.

In case it is desiredto convert say one fourth of the available chlorine to hypochlorite, it would nevertheless be advantageous to supply tower 5 with the full amount of water necessary forcomplete absorption of the chlorine. The final stage of pressure reduction is then maintained at a pressure high enough to allow thewater leaving to retain asufficient amountoi chlorine that the vapor pressure of the chlorine therein will be equal to one fourth the partial pressure of chlorine in the gas entering tower 5. In this manner the absorption of more than three fourths of the chlorine in tower '5 is prevented leaving one fourth available for the production of hypochlorite. Since the chlorine recovered as such is then fed to the evactors at the highest possible pressure, the water vapor entering the evactors will be a minimum. A smaller amount of motive steam is then required for the compression of thechlorine itself to atmospheric pressure-and the useless compression of water vapor is reduced to aminimum.

In the event that the partial pressure of chlorine in the inlet gas is so low that the pressure necessary to liberate a substantial proportion of chlorine from the solution approaches the vapor pressure of water at the temperature of the inlet solution, the use of a single stage of evaporation may sufllce.

Various changes may be made in the form and arrangement of the apparatus as well as in the details of procedure without departing from the invention or sacrificing the advantages thereof.

I claim:

1. The method of recovering chlorine from a mixture of gases in which chlorine is the major constituent most readily soluble in water,. which comprises washing the gas mixture with water to dissolve chlorine therein, subjecting the resulting chlorine solution to successive chlorine vaporization operations at successively reduced pressures below atmospheric pressure, and adding steam to the solution in the final vaporization operation in an amount sufficient to maintain the temperature of the solution during such vaporization oper- 6 ation at substantially the temperature of the solution entering said vaporization operation.

'2.v The method of recovering chlorine from amixture of gases in which chlorine is the major constituent, most readily soluble in water, which comprises washing the gas mixture with water to dissolve chlorine therein, subjecting the resulting chlorine solution-to a pressure lower than the partial pressure of chlorine in the original gas mixture to vaporize a substantial portion of the chlorine together with some water, subjecting the partially dechlorinated solution to a lower pressure not below the vapor pressure of water at the temperature of the partially dechlorin-ated solu-. tion to vaporize a further portion of the chlorine together with some water, and adding steam to the solution in the final vaporization operation in an amount sufficient to maintain the temperature of the solution during such vaporizationoporation at substantially the temperature of the solution entering said vaporization operations- 3. The method of recovering chlorine from a mixtureof gases in which chlorine is the major constituent most readily soluble in water, which comprises washing the gas mixture with an aqueous medium from the class consisting of water and dilute solutions of chlorine in water to dissolve chlorine therein, subjecting the resulting chlorine solution to a pressure lower than the partial pressure of chlorine in the original gas mixturetov-aporize a substantial portion of the chlorine tog'ether with some water, subjecting the partial-. ly dechlorinated solution to a lower pressure not below the vapor pressure of water at the temperature of the partially dechlorinated solution to vaporize a further portion of the chlorine together with some water, adding steam to the solution in the final vaporization operation in an amount suflicient to maintain the temperature of the solution during such vaporization operation at substantially the temperature of the solution entering said vaporization operation, and utilizing the resulting dec'hlorinatedsolution as the aqueous medium to wash the original gas mixture.

4. The method of recovering chlorin from a mixture of gases in which chlorine is the major constituent most readily soluble in water, which 'compriseswa-shingthe gas mixture with water to dissolve chlorine therein, subjecting the. resulting chlorine solution to a pressure lower than the partial pressure ofch-lorine in the original gas mixture to vaporize a substantial portion of the chicrine together with some water, subjecting the partially. dechlorinated solution to a lower pressure not below the vaporpressure of water 'at the temperature o f.-the partially dechlorinated solution to vaporize a further portion of the chlorine together with some water, adding steam to the solution in the final vaporization operation in an amount sufilcient to maintain the temperature of the solution during such vaporization operation at substantially the temperature of the solution entering said vaporization operation, and condensing the water vapor admixed with the vaporized chlorine 'to obtain substantially water- 7- tu-re to vaporizeasubstantial-portion. of: thee chin .v rine togetherwwith'someawater;subJectingtthe partiallyrdechlorinatedsolution to alower pressure not below the vapor pressure of waterat-the'tem per-atureof the partially deohlorinated solution to vaporize a furtherportion of the chlorinetogether with-some watenf adding steam-to flie -solution in the final vaporization operation in an --amount suflicien-t to :maintaintthe temperature of the :so-

water rmixture from the first vaporization; contdensing' the water vapor in such mixture-to obtain zcsubstantialiy water-free chlorine; and re turningotheresulting condensate 't-o thefirst va-- porizaation;

6. "The method ofrecovering- 'chlor-inefrom a mixture :of gases' in which chlorine is the: major constituent most-readilysoluble in -Water,- which comprises washing the gas mixture *Withwater to dissolve chlorine therein; subjecting the resulting chlorinesolutionto azpressure lowerth'an the pa-rtial pressure of'ch'lorineni'the original gas mix-v turebut higher thamt-he vapor pressureof water at theztempera-ture ofsuch 'sol'utionto vaporize a substantial portion of the chlorine together-with some waterirsimultaneously supplying heat to the solu-tioninran amount'sufiicient to prevent-a substantial-flowering :"Of the temperature --thereof, withdrawing the ":vaporizedchlorine and water;

and 'condensing the waten vapor and-recoveringchlorine from the withdrawn:vaporized chlorine and water.

7. The method of recovering chlorine from a mixture of gases in which chlorine isthe major constituent most readily'isoluble in 'water,"which' comprises washing the gas mixture? with water to dissolve chlorine therein, subjecting'the resulting chlorine solution to a pressure lower than the partial "pressure of-chlorine in=the-original gas mixture but higher than the "vapor pressure "of watera't the temperatureof suchsoluti'onto va porize a substantial portionpftthe chlorine together with some water,-- simultaneously supply-- inghe'at to the solution an amountfs-uflicient to-prevent'a substantial loweringof the tempera ture thereof, Withdrawing 'the'vaporized 'chlorine'- andwater, condensing the'water-vapor and "re- 8- covering zohlorine from the withdrawn vaporized chlorine and water, and returning the condensed water'vapor-to be utilized in thevsubsequent washing of further amounts of theagas mixture.

8. -The- --method of.recovering chlorine from a. mixture ofgasesin which chlorine is themajor constituentmostreadily soluble in waten-which comprises washingthe-gas mixture with anaqueous medium firom'the class oonsistingof water and, dilute-solutions of chlorine in water'under such conditions as to --dissolve only a portion of the chlorine therein, withdrawing aneffluent-gas :mixture containing the u-ndissolved chlorine; subjecting the resulting "ohlorine solution to successive chlorine-vaporization operations at successively reduced pressures below atmospheric pressure, adding-steam to the solution in the final vaporization operationin anamount suffic-ient to maintain the temperature of the solution during' suchvaporization operation at substantially the tomperature of the solution entering said vaporization operation; the final vaporization operation being conducted under a pressure sufllciently highothat the aqueous :rnedium leaving said operation twill contain a relatively small amount of chlorine comparedto' the amount of chlorine contained in the. aqueous medium resulting irom said-washing; operation;"returningtheaqueous medium leaving s aid final' vaporization *.--operation to the washing operation and thereusing'it as the aqueous 'mediumto washfurther-amounts 'of the originaL gas mixture, and reacting thB' UIId-lSSOIVEd' chlorine in the-withdrawn'efliuent gas mixture with amate-. rial capable of forming a: hypochlorite.

. FREDERICK -R. =BALCAR.

REFERENCES CITED I ThefolloWing I'GfGIGI-ICBSfaIG of record in the file bf this' 'patent'. I i

' UNITED STATES '.PA'IENTS' 7 Number- 'Name' Date "1,418,002 Kothny- May 30,1922 1,422,183 Curme'"; Ju1y"1i1, '1'922 1,809';441 fEliiott' 'June'"9,'1931" 250611332 'Rue Nov-.17, 1936 "2,1445692 Schuf't'a'n Jan. 24, 1939 2,169,210 1 *Bal-c'ar Aug. 15, 1939' 2206,490 Tr'amm July-=2, 1940 2242323 "Powell May 20, I941 2250,925 Bohcoclc; Ju1y'29,"1'941 2,320,635 Mericola June 1, I943 FOREIGN PATENTS Number Country Date 15,483 Great- Britain i886. 

